Intravascular doppler ultrasonic device and method for controlling its operation

Abstract

An intravascular Doppler ultrasonic device comprises a tip region forming a fraction of a catheter body at a distal end thereof and carrying an ultrasound probe. The tip region is bendable in a direction perpendicular to a longitudinal direction. An actuator is provided in the tip region, which is configured to receive actuation drive power provided through the catheter body and to exert to the tip region a bending moment of a controllable amount. An actuation controller is configured to control actuation drive power delivery to the actuator so as to control the amount of the bending moment. A Doppler spectrum analysis unit is configured to receive Doppler spectrum data and to determine from it a Doppler signal quality measure indicative of a signal quality of the Doppler spectrum. The actuation controller is configured to determine the actuation drive power in dependence on the determined Doppler signal quality measure.

The invention claimed is: 
     
       1. An intravascular Doppler ultrasonic device, comprising:
 a catheter body shaped for intravascular insertion into a blood vessel of a living being, wherein the catheter body comprises:
 a tip region forming a fraction of the catheter body at a distal end thereof; and 
 a region proximal of the tip region and extending along a longitudinal direction, wherein the tip region is bendable in at least one direction perpendicular to the longitudinal direction; 
 
 an ultrasound probe in the tip region, which is configured to emit ultrasonic radiation from the distal end of the catheter body and to receive ultrasound echo radiation and provide a probe signal indicative thereof, wherein the ultrasound echo radiation comprises a Doppler frequency shift; 
 a Doppler spectrum determination unit, which is configured to receive the probe signal and to determine therefrom a Doppler spectrum data indicative of a Doppler spectrum of the ultrasound echo radiation; 
 an actuator in the tip region, which is configured to receive actuation drive power provided through the catheter body and to exert to the tip region a bending moment of a controllable amount; 
 an actuation controller, which is configured to control actuation drive power delivery to the actuator so as to control the amount of the bending moment; 
 a Doppler spectrum analysis unit, which is configured to receive the Doppler spectrum data and to determine from it a value of a Doppler signal quality measure indicative of a signal quality of the Doppler spectrum, wherein the Doppler signal quality measure is different from the Doppler frequency shift; 
 wherein the actuation controller is further configured:
 to determine the actuation drive power in dependence on the determined value of the Doppler signal quality measure; 
 to control a scanning motion of the tip region within a predetermined scanning range by controlling the actuator for consecutively setting a plurality of bending moments; 
 to associate each bending moment of the plurality of bending moments with a different value of the Doppler signal quality measure; 
 to determine, based on the determined value of the Doppler signal quality measure, whether the signal quality of the Doppler spectrum exceeds a threshold; and 
 to determine the bending moment to be used for operation by selecting a bending moment which is associated with the determined value of the Doppler signal quality measure. 
 
 
     
     
       2. The intravascular Doppler ultrasonic device of  claim 1 ,
 wherein the Doppler spectrum analysis unit is configured to determine the value of the Doppler signal quality measure at least once per cardiac cycle of the living being, and 
 wherein the actuation controller is configured to adjust the bending moment in a subsequent cardiac cycle if the signal quality of the Doppler spectrum exceeds the threshold. 
 
     
     
       3. The intravascular Doppler ultrasonic device of  claim 1 , wherein the Doppler spectrum analysis unit is configured to determine the value of the Doppler signal quality measure by determining and using at least one of the following quantities for calculating the Doppler signal quality measure:
 a Doppler zeroth moment of the spectral power of the received ultrasound echo radiation; 
 a Doppler first moment of the spectral power of the received ultrasound echo radiation; 
 a Doppler second moment of the spectral power of the received ultrasound echo radiation; 
 a pulsatile index, or 
 a resistive index. 
 
     
     
       4. The intravascular Doppler ultrasonic device of  claim 1 , wherein the ultrasound probe is configured to emit the ultrasonic radiation and provide the probe signal continuously. 
     
     
       5. The intravascular Doppler ultrasonic device of  claim 4 ,
 wherein the actuation controller is configured to control a bending motion of the tip region for continuously scanning across a range of different bending positions; and 
 wherein the Doppler spectrum determination unit is configured to continuously provide the value of the Doppler spectrum data determined for the different bending positions; 
 further comprising:
 a Doppler spectrum selection unit, which is configured to select only that Doppler spectrum data which is associated with those bending positions that result in a signal quality of the Doppler spectrum that exceeds the threshold; and 
 a graphical user interface, which is configured to receive and display the selected Doppler spectrum data. 
 
 
     
     
       6. The intravascular Doppler ultrasonic device of  claim 1 , wherein the actuation controller is configured to control a bending motion of the tip region across a range of bending positions, to determine a motion response measure indicative of a difference between the values of the Doppler signal quality measure determined at different ones of the bending positions, and to interpolate to the optimal velocity profile. 
     
     
       7. The intravascular Doppler ultrasonic device of  claim 1 , wherein the actuator comprises an electrically controllable shape-changing material, which is mechanically coupled to the catheter body in the tip region and configured to cause the bending moment by a shape change in response to receiving the actuation power. 
     
     
       8. The intravascular Doppler ultrasonic device of  claim 7 , wherein the actuator comprises at least one actuator layer made of an electroactive polymer material that is attached to a flat catheter core of the catheter body, and wherein the actuator layer is configured to expand in-plane in response to receiving the actuation power. 
     
     
       9. The intravascular Doppler ultrasonic device of  claim 7 , wherein the actuator comprises at least one actuator wire made of a shape memory alloy that is attached to a catheter core, and wherein actuator wire is configured to change its temperature in an amount that depends on an amount of actuation power received, and to change its shape in response to the temperature change. 
     
     
       10. The intravascular Doppler ultrasonic device of  claim 7 , wherein the actuator comprises at least one actuator layer made of a bi-metal that is attached to a flat catheter core of the catheter body, and wherein the actuator layer is configured to expand in-plane in response to receiving the actuation power. 
     
     
       11. The intravascular Doppler ultrasonic device of  claim 1 , wherein the actuator comprises at least one first actuator layer made of an electroactive polymer material that is attached to at least one second actuator layer made of a shape memory alloy. 
     
     
       12. A method for controlling operation of an intravascular Doppler ultrasonic device, the method comprising:
 controlling emission of ultrasonic radiation by an ultrasound probe from a distal end of a catheter body, for receiving ultrasound echo radiation, and receiving a probe signal indicative thereof, wherein the ultrasound echo radiation comprises a Doppler frequency shift; 
 determining and providing Doppler spectrum data from the probe signal, the Doppler spectrum data being indicative of a Doppler spectrum of the ultrasound echo radiation; 
 controlling actuation drive power delivery to an actuator in a tip region forming a fraction of the catheter body at the distal end thereof, wherein the catheter body comprises:
 the tip region; and 
 a region proximal of the tip region and extending along a longitudinal direction, wherein the tip region is bendable in at least one direction perpendicular to the longitudinal direction, so as to drive exertion of a bending moment of a controllable amount to the tip region; and 
 
 wherein controlling actuation power delivery comprises:
 receiving the Doppler spectrum data and determining from it a value of a Doppler signal quality measure indicative of a signal quality of the Doppler spectrum, wherein the Doppler signal quality measure is different from the Doppler frequency shift, 
 determining the actuation drive power in dependence on the determined value of the Doppler signal quality measure; 
 controlling a scanning motion of the tip region within a predetermined scanning range of different bending positions by controlling the actuator for consecutively setting a plurality of bending moments; 
 associating each bending moment of the plurality of bending moments with a different value of the Doppler signal quality measure; 
 determining, based on the determined value of the Doppler signal quality measure, whether the signal quality of the Doppler spectrum exceeds a threshold; and 
 determining the bending moment to be used for operation by selecting that bending moment which is associated with the determined value of the Doppler signal quality measure. 
 
 
     
     
       13. The method of  claim 12 , further comprising:
 controlling a bending motion of the tip region for continuously scanning across the scanning range; 
 providing the Doppler spectrum data determined for the different bending positions; 
 selecting only that Doppler spectrum data which is associated with that bending position which is associated with the determined value of the Doppler signal quality measure indicative of the highest Doppler signal quality; and 
 controlling display of the selected Doppler spectrum data via a graphical user interface. 
 
     
     
       14. A computer program for controlling operation of an intravascular Doppler ultrasonic device, comprising executable code for executing the method of  claim 12  when executed by a processor of a computer.